Ship&#39;s stern



Aug. 16, 1938'.

v. YOURKEVITCH SHIPS STERN Filed Aug. 2, 1955 INVENTOR.

ATTORNEY.

Patented Aug. 16,1938 2,127,475

UNITED STATES PATENT orrlcs 2.12am srnrs s'rEa'N Vladimir Yourlrevitch, Paris, France Application August 2, 1935, Serial No. 34,331 In France December 6, i934 2 Claims. (Cl. 114-5d) This invention relates to the hulls of ships and nal movement of the hull isthus lessened and is directed to novel configurations in the stem the speed materially increased without change in or aft portion thereof and more especially below driving horsepower of the vessel. the waterline. Another object of the present invention, de-,

One object of the invention is to stiffen the sirable in all hulls, but particularly in hulls of aft portion of propeller driven ships in such manfast moving vessels, is to increase the efficiency of ner as to minimize vibration resulting from the the propellers by properly directing the flow of operation of the propellers and from other water past the hull in such manner that it is causes. This vibration, which is particularly no fed to the propellers in the most emcient way. ticeable at certain speeds, is very annoying and Various expedients have been resorted to in hull 10 uncomfortable because of its persistency and this construction to this end, but the majority of persistency of vibration becomes, with time, them which seek to direct the flow of water to prejudicial to shell plating and structure of the the propellers counteract any increased eflicienc'y ship. thereof by the building up of increased resistances My experiments and research in this connecto forward movement of the hull. For example, 15 tion have convinced me that this difliculty is it has been proposed to fit all sort of fins guidlargely due to the inherent properties of hull ing water towards propellers or to broaden the construction as heretofore designed and which hull directly forward of the propellers in various result in hull forms having appreciable overhang waysyin order to cause the water to be drawn at the stern, making it impossible to properly inwardly back of such enlargements and into brace said stern portion or incorporate therein the grip of the propellers, but these expedients, the desirable inherent buoyancy or displacement. although tried in various ways, have not proven As a result, the stern portions of ships, in the satisfactory and they tend to slow down the boat great majority of cases, project in an aft direcdue to increased resistance.

:5 tion beyond the buoyant body of the hulls and The present invention accomplishes eiiicient this constitutes an ideal condition for vertical propeller operation in a thoroughly satisfactory and lateral whip, particularly in overhang porway and through the formation, within the contions of the hull. tour of the hull below the waterline, of channels With these considerations in mind, the present which extend fore and aft and are of convergentinvention provides for materially increased londivergent contour, so as to produce, in effect, a

gitudinal and lateral stiflness and rigidity of substantially Venturi contour channel at each the stern portion of the hull, so as to properly side of the hull, so that, as the hull of the ship reinforce the same against lateral whip as well moves forwardly, the water streams flow smoothas vertical vibration. ly through these channels with a minimum width 5 Another object of the invention is to increase of hull cross section between them. These the speed of ships of the faster type, through the streams unite back of the rudder, which isinemployment of novel stern construction. This terposed between said streams, in long flowing object of the invention, has to do,-more particulines, so as not to set up eddies or result in aplarly, with naval destroyers, cruisers and the preciable resistance.

40 like, which travel at express speeds, although The propellers are mounted to partially pro- 40 this feature will also be of advantage in fast iect within said channels and are preferably 'juxships, other than naval vessels. For example, taposed with contracted section of the above when a destroyer is traveling at high speed, it channels so as to cause the propeller tips to has a pronounced tendency to squat at the operate sensibly within the channels gullets and stern. In other words, the bow appreciably rises, so as to receive the water streams in a most efli- 45 while the stern correspondingly lowers in the cient way. Contraction of the water'flow by these water, thus causing a partial up-ending of the Venturi-like channels produces sidewise an inhull which, in case of an exaggerated squatting, jector action on the adjacent water streams increases its resistance to passage through the which are drawn in a wide flow towards the pro- M) water. The present invention, when adapted to pellers, the emciency of which is materially inhulls of this character, serves to so increase the creased because of this accelerated flow of water. buoyancy of. the stem or aft portion of the hull An important feature of this invention resides as to minimize this settling efiect at high speeds. in the formation of what may be termed a buiin order that the hull may be maintained at bous cross section at the keel, in the vicinity of a more even keel. Resistance against longitudithe propellers, and extending forwardly and aft 55 therefrom and. tapering off in both directions into a substantially torpedo shape. Such a bulbous formation at the keel produces several of the advantages to which I have hereinbefore referred. When made of the tapering form, simulating a torpedo shape, instead of materially increasing the resistance to forward movement of the hull as all other water-guiding protuberant devices, such as deflectors, fins, nozzles, etc., invariably occasion, this bulbous keel formation reduces on the' contrary the resistance. At the same time it increases the buoyancy through increased displacement of the stern portion of the hull. It reduces the so-calied squatting. It allows of proper reinforcement of the stern portlon'of the hull by providing backbone at the keel, so as to minimize vertical or lateral vibration or whip. It permits of the narrowing of the hull in the vicinity oi the water line, in view of a further reduction of the resistance, the deficient displacement on the water line being counterbalanced by the additional displacement of the bulbous keel formation. It provides a convenient means for the formation'of the convergent-divergent channels to which I have referred and it provides additional fuel or cargo space if this is desired. It also may be utilized to serve as a water ballast tank, through the regulation oi the contents of which the hull may be properly "trimmed" in a fore and aft direction. Furthermore, when so used, the ballast is at the keel where it is most efficient in preventing rolling or wallowing in a heavy sea or cross swells.

Another important feature of the present invention, aswill hereinafter be more fully described, resides in the reinforcing of the keel at the stern, as hereinbefore explained, so that the lower end of the stern post may be properly anchored and an enclosed rudder used, which rudder may be either of the balanced or unbalanced type.

Features of the invention, other than those adverted to, will be apparent from the hereinafter detailed description and claims, when read in conjunction with the accompanying drawing.

The accompanying drawing illustrates one practical embodiment of the invention, but the drawing is to be understood as illustrative, only, and not as defining the limits of the invention.

- Figure 1 is a side elevation of a stern of a conventional hull.

Figure 2 shows plan traces of the stern portion and waterline contour of the hull portion of Figure 1.

Figure 3 shows the so-called body plan or vertical traces of several transverse frames of the hull indicated in Figure 1.

Figure 4 is an outline cross section taken at the section line 44 of Figure 1 and showing deck lines, shell plating and waterline.

Figures 5 and 6 give a simplified image of the mechanical properties of the stern section of the hull of Figure 1.

Figures 7, 8, 9 and 10 correspond to Figures 1, 2, 3 and 4 of the drawings of a conventional hull, but show a hull embodying the present invention.

Figure 11 corresponds to'Figure 5 but gives a simplified image of the mechanical properties of the hull of the presentinvention.

Figure 12 is a comparative graph of the areas of cross sections of the hull and of the weights or loadings of different hull constructions.

It is felt that the present invention may be best understood if explained in connection with dicated by the reference character i0, and the 4 contours of which hull are not only narrowed in the vicinity of the load waterline II, in view of reduction of the resistance, as will be apparent from the successive equidistant transverse sections or frames indicated at I, 2, I, 4 and 5 in Figures 1-3, but also are tapered upward aft in vertical plan for the same purpose.

When a hull is thus narrowed and formed as shown, it will have an appreciable overhang at the stern and in practice, it may be likened structurally to a spring l2, as shown in Figure 6. This spring has superimposed leaves l3, l4, l5, etc. rendering the same vertically resilient as it extends from its zone of anchorage IS. The overhanging stern of the hull of Figures 1 and 2 possesses the same broad peculiarities because the ship construction is unavoidably of a more or less resilient nature and possesses some "give when made as described, as the overhang stern portion must be of a light construction and does not allow of sufficient internal bracing to make it rigid. As a result, the stern of the ship of Figure 1 will vibrate vertically under the action of the propellers indicated at I! and under buffeting of the seas. Similarly, since the stem is relatively narrow, particularly below the waterline ii, this portion of the hull will have an inherent tendency to weave or whip laterally due to the operation of the propellers and to the passage of water streams pastthe rudder.

Graphically, the cross section of the hull, at the section line 4--4 of Figure 3, may be compared, for practical purposes, to a girder section, such as shown in Figure 5, in which the upright web i8 corresponds to the vertical dimension of the hull, while the flanges i9 and 2| correspond to the decks or other internal bracing. This section is taken in the vicinity of the propellers but aft of this the vertical dimension of the hull decreases rapidly until it is relatively shallow. Thus a girder of the kind shown will be susceptible to appreciable vertical deflection as well as appreciable lateral deflection, particularly in the lower portion of the web I! thereof,

under the actionof the propeller and the other forces to which I have referred and this deflection will of course increase progressively aft. This is one reason for pronounced vibration in the stern of ships as now constructed and, prior to this invention, no adequate solution has been found to minimize the same to a point where it will not be uncomfortable to the passengers or where it will not produce undesirable strains on the hull structure. The present invention solves this problem in a simple and efllcient manner.

Thus, as shown in Figures 7-11, the rear frames, at the successive transverse sections i, 2, 3, 4 and 5 are formed with appreciable hollows accentuated in the region of the load waterline ii and end in the region of the keel in pronounced bulbous contours formed by club-footed frames and indicated generally at 2|. The

"traces shown result in a bulbous keel portion in- (8 dicated generally by the reference character 22,

which tapers fore and aft from its greatest vertical and horizontal dimensions, so that it may be said to be substantially torpedo shapein a longitudinal direction of the hull. This so-called bulbous portion may vary in cross section without departing from this inventiombut I preferably make the same substantially in the shape of a waterdrop, as shown in Figure 10, whereby the superimposed portion of the hull is joined to the bulbous keel portion 22 by a relatively thin intervening submerged section 24' producing a substantially hour glass section to form, at either side thereof, channels 24 which extend longitudinally of the hull. By virtue of the formation of the superimposed structure and the underlying bulbous portion, these channels converge rearwardly from their forward open ends to a point of minimum dimension, indicated generally by the region 23 in longitudinal view, and aft of this region the channels flare out rapidly so as to produce, in each, a divergent-convergent longitudinal-contour, somewhat similar to a longitudinally sectioned Venturi tube of which the outer half is removed. The propellers, shown as twin propellers, and indicated at I], are positioned in the region of minimum dimension of these channels and are so mounted, as illustrated in Figures '7 and 10, as to project into and operate within the channels.

It will thus be noted that the hollowing out and club-footing of the frames as stated produces the two convergent-divergent semichannels leading to and from the propellers and these function after themanner of nozzles for the induction of water to the propellers and the discharge of water therefrom. In practice, the said channels smooth out the water streams and lead them to the propeller from a point below,

so as to permit the propellers to operate with the greatest efficiency and at the same time minimize the drag of surface water into the propellers with resulting absorption of air bubbles and fall of efficiency of propellers. In fact, it is found that the propellers tend to suck the water longitudinally of the channels and produce a pronounced suction therein which materially decreases resistance to the forward passage of V the hull, while the water leaving the propellers is discharged through a rapidly diverging space directly to the rudder. This directed water flow produces an increased reaction on the stern of the hull and contributes to forward progression of the ship. Thus, instead of increasing the resistance to the movement of the ship, as has heretofore been the case with all known means of directing water to the propellers, the structure of the present invention decreases this resistance considerably, so that I am able to fullyutilize the increased efficiency of the propellers for the forward movement of the hull."

By positioning the propellers above the bulbous portion, so as to project into the channels, I further produce a condition particularly propitious for the support of the outboard ends of the propeller shafts. Heretofore the outboard ends of these tail shafts have been carried by propeller struts forming parts of brackets which are riveted exteriorly to the hull in depending position and generally each comprises two V shaped arms arranged in angular relation to one another at a relatively acute angle, as shown in Figure 4 at 28'. This arrangement does not produce a rigid mounting. By reference to Figure 10, however, it will be noted that the arms of the struts 'not occur and the ship is, in

28 of the present invention are positioned in substantially right angular relation to one another and at the same time substantially normal to the surfaces of the=portions of the hull to which they are fixed, so as to more effectually support the shaft bearings. This arrangement is made possible by the rugged bulbous portion which is sufllcientlystrong to withstand the lateral thrust and constitutes in effect the backbone of the ship at this point.

The bulbous keel portion 22 preferably extends substantially to the stern post 25 which instead of being composed of assembled 'pieces of cast iron of complex design and shape as heretofore, may be conveniently formed, according to the present invention as shown in Figure 7, with the stern post carried around and anchored to the aft end of the bulbous portion which constitutes a firm anchorage therefor. The rudder 26 may be mounted, as shown, within the confines of the stern post and properly contoured in the usual way.

Another advantage of this stern post arrangement is that it ties together the aft end of the bulbous portion and the extreme stern of the hull and assists in producing an efficacious reinforcement of the entire stern of the hull. It will of course be understood that the stern post may be shaped otherwise than as shown in Figure '7, but it preferably is carried well down to the keel and anchored to the bulbous portion 22 as stated.

When the hull is formed, as shown in Figures 7-10, it will be noted that a mechanical result illustrated in the girder form of Figure 11, is produced as compared to the structure shown in Figure 5. In Figure 11, the web 18 of the girder is deeper and in addition to the decks l9 and 20, the web of the girder is provided at its lower edge with additional lateral flanges 21, which are of appreciable width and indicate the structural strength or reinforcement factor of the bulbous part 22. This additional flange 21 manifestly not only increases the strength and rigidity of the increased web height, but it also very materially increases these factors in a lateral direction. In other words, it gives the ship backbone in its aft end at the keel andpreciudes lateral whip of this part of the ship and at the same time reinforces the same against vertical,

ures 7 and 8, is directly forward of the stern post or as far aft as possible. This I have found to be of pronounced advantage. For example, in conventional ship design for fast ships, there has invariably been a narrowing of theafter portion with the object of decreasing the resistance to forward motion; This naturally decreases the buoyancy of this aft extremity, so that there is a tendency of the ship to squat or lower in the water; particularly when the ship is traveling at high speeds. With the additional buoyancy however aiforded by the bulbous portion 22, this does contradistinction, maintained on a more even keel. This holds good not only for a vessel traveling in smooth ,water,

but also cutting through the seas in which'case the torpedo shaped bulbous formation acts as a kind of anti-pitching device.

The showing of Figure 12 graphically illustrates these distinctions by comparison. In this figure, A represents the graph of the areas of the cross sections of the stern; this graph also represents, on a suitable scale, the graph of the displacements or the buoyancies of the corresponding parts of the ship. The broken line P represents the repartition of the weights along the ship, the total areas delimited by graphs A and P being equal for the entire ship, because the displacement of a floating body is equal to its weight. Finally C is the graph of the loads which result from the diil'erences of the ordinates of the graphs A and P, the areas delimited by graph C representing in each transversal part the local excesses of the weight over the displacement, when they are located below the horizontal axis CY, and the local excesses of the displacement over the weight, when they are located above this axis. It can be seen that at the extreme rear end of the ship the weights overcome the buoyancy (hatched area L, Figure 12), and, as these weights are located at a great distance from the middle of the ship and therefore act on along arm of the lever, they produce considerable pitching moments. The bulbous protuberance in the shape of a torpedo, formed, in accordance with the invention by the club-footing of the stern frames, oompensates for this excess of weight by increasing the displacement and thus decreases the pitching moments by the buoyancy oi the stem. The graph of the areas of the cross sections A, instead of joining itself tangentially to axis OY, produces an enlargement M, as represented by the dot and dash line in Figure 12; the hatched area K, located in this region between branch M and the old graph A, must be equal or superior to the hatched area L, representing the excesses of the weights. Moreover, by utilizing the enlargement or bulbous part 22 of the bow and the stern as a water ballast chamber, it is possible to regulate, at will, the weight of the stern part and thus the trim of the ship.

The present invention is preferably built into ships during the initial construction thereof, but

it may be also incorporated in old ships by removing the stem section of the hull and building on a new section embodying the invention. This new section may be so designed as to increase the length of the hull sufllciently to incorporate thereintothe present invention, although, if desired, more extensive portions of the aft section of the hull may be remodeled, although this is generally not desirable as it will materially increase the cost over and above that of the lengthening operation, which does not require appreciable modification of the remaining frames of the hull. The foregoing detailed description sets forth the invention in its preferred practical form, but the invention is to be understood as fully commensurate with the appended claims.

"Iapering" and tapered", as used in the appended claims, means a gradual diminution of thickness.

Having thus fully described the invention, what I claim as new and desire to secure by Letters Patent is:

1. A ship's hull provided aft of amidships and forwardly oi the stern post with a bulbous keel portion, a superimposed buoyant portion, and an interposed upright portion of cross section having concave sides which merge into the corresponding sides of the superimposed portion in substantially tangential relation thereto, said bulbous keel portion tapering both' fore and aft from a point intermediate its ends to form, at both sides of said interposed portion, convergent-divergent channels extending in a fore and aft direction, propellers partially projecting into said channels stantially with the region of minimum cross section of said upright portion, and a stern post, the lower end of which is anchored to the aft end of said bulbous keel portion in substantially tangential relation thereto.

2. A ship's hull provided aft of amidships with a bulbous keel portion tapering in fore and aft directions, and a stern post anchored to the after end of the bulbous keel portion and extending rearwardly and upwardly in substantially tangential relation to the keel.

VLADIMIR YOURKEVITCH.

materially reduced and juxtaposed sub- 

